This lesson describes the mechanisms of ventilation and gas exchange in insects. The PowerPoint and accompanying worksheets are the part of the second lesson in a series of 2 lessons which have been designed to cover the details that are set out in point 3.1.1 (f) of the OCR A-level Biology A specification. The first lesson in this series describes ventilation and gas exchange in bony fish
In the previous lesson, the students were introduced to the different circulatory systems of mammals and bony fish and this knowledge is checked upon at the start of this lesson. This is relevant because the open circulatory system of an insect explains how oxygen is not transported in the blood but instead is absorbed from the body fluid that bathes the tissues. The next part of the lesson describes the structure of the spiracles, tracheae and tracheoles in the tracheal system and explains how this system is responsible for the delivery of oxygen to the open end of the tracheole for gas exchange with this fluid. As the tracheae are supported by chitin, which is similar in structure and function to cellulose and keratin respectively, a series of exam-style questions are used to challenge the students on their knowledge of those polymers from module 2.1.2 (biological molecules). As always, the mark scheme is embedded in the powerpoint so students can assess their understanding and progress. The final part of the lesson describes how squeezing of the tracheoles by the flight muscles and the changes in the volume of the thorax as a result of the movement of the wings are similar to mechanisms observed in mammals.